What does Revelation 21:22 mean?

In Old Testament times, the Israelites worshiped God in a temple, but New Jerusalem doesn't need a temple because the entire city is the dwelling place of Almighty God and the Lamb. In Old Testament times God's presence graced a temple in Jerusalem. It was the center of Jewish worship for centuries before the exile, when it was laid waste by the Babylonians. When a delegation of Jews returned from captivity, they rebuilt the temple in Jerusalem (Ezra 6:13–18).

Although no temple is located in this heavenly New Jerusalem, a temple exists on earth in Jerusalem during the millennium. Malachi 3:1 predicts part of this end-times victory, saying "And the Lord whom you seek will suddenly come to his temple." Zechariah 14:16 predicts that survivors of the nations that launch an assault on Jerusalem will "go up year after year to worship the King, the LORD of hosts, and to keep the Feast of Booths." These concepts of worship and festivals imply the existence of a temple in Jerusalem during the millennium.

This lack of an explicit temple also reinforces the new covenant promised by God in Jeremiah 31:31–34, which indicates a direct relationship between man and God.